Dryer for photographic type emulsion coated sheets



Nov. 22, 1966 H. N. FAIRBANKS ET AL 3,286,367

DRYER FOR PHOTOGRAPHIC TYPE EMULSION COATED SHEETS Filed Oct. 4, 1963 5Sheets-Sheet 1 41 CONTROL l F/G. POWER -/7 SOURCE DAN/E L H. ROBBINSHENRY IV. FAIRBANKS I NVENTORS ATTORNEY NOV. 22, 1966 H FMRBANKS ET AL3,286,367

DRYER FOR PHOTOGRAPHIC TYPE EMULSION COATED SHEETS 5 Sheets-Sheet 2Filed Oct. 4, 1963 DAN/EL h. ROBBINS HENRY N. FAIRBANKS INVENTORS BY g7&

ATTORNEY NOV. 22, 1966 FAlRBANKs ET AL 3,286,367

DRYER FOR PHOTOGRAPHIC TYPE EMULSION COATED SHEETS Filed Oct. 4, 1963 5Sheets-Sheet 3 DAN/E L H. ROBBINS HENRY N FA/RBA/VK5 I NVENTORS ATTORNEY.hydrophilic.

United States Patent p 3 286 367 DRYER FOR rHoToRAPHIO TYPE EMULSIONCOATED SHEETS Henry N. Fairbanks and Daniel H. Robbins, Rochester,

N.Y., assignors, by mesne assignments, to Itek Corporation, Lexington,Mass., a corporation of Delaware Filed Oct. 4, 1963, Ser. No. 313,880 7Claims. (Cl.34-123)' The present invention relates to an improvedapparatus for drying emulsion coated carrier sheets. More particularlythe invention is related to a dryer for photographic processingprojection offset plates suchas the typefmarketed by the assignee underthe trademark Project-A- Lithf This material is a silver halide emulsionon a support, which upon development results in an image area which isoleophilic and a non-image area which is The automaticprocessor of thetype disclosed in the copending application has as one of its features,the ability to produce offset platesat a rapid rate. The devicedisclosed therein is capable ofproduc'ing offset plates on a continuousbasis at the rate of approximately two per minute. In order to maintaina two per minute overall continuous production rate, it is desirablethat a compatible dryer operate at the same rate. Coupled with theproblem of relatively short drying time is the relatively low maximumtemperature at which the offset plate becomes adversely affected. Theoffset plate is a plastic coated carrier sheet having an emulsioncoating on one of the plastic coated sides. Both the plastic andemulsion have relatively low softening temperatures, e.g. in the orderof 185 F. If either material is heated above these temperatures it wouldtackify and stick to the transport and dryer. In addition when theemulsion temperature rises above a critical level, eg l70-l90 F., itdiscolors, whereby the plate quality is deteriorated. In addition toquality being affected by excessive temperature, it has also beenobserved to be affected by the uniformity with which drying occurs. Someof the other problems associated with the drying of this type ofmaterial arise due to the softness of the emulsion as it emerges fromthe processor. Therefore, transporting the plate through the dryer mustbe accomplished without marring or embossing the emulsion surface,whereby the plate quality will be deteriorated. Dryers known in the artdo not produce the uniform, rapid drying, at controlled lowtemperatures, without physical damage to the emulsion that is requiredinthe drying of a material such as Proje-ct-A-Lith.

Some prior art devices use heated air for drying photographic typeemulsions. One such device is shown in U.S. Patent No. 2,869,246 issuedJanuary 20, 1949 to Walter Buschmann and Walter Buhren. Devices of thisgeneral type require large volumes of air available at the emulsionsurface in order to keep the emulsion temperature relatively low and atthe same time drying rapidly to match the Output of an automaticprocessor of the type disclosed in the assignees copending application.Other dryers for photographic type emulsions, transport the sheet on aweb over a heated drum. The web absorbs any chemical left on the surfaceof the plate after processing. The gradual build-up of these chemicalsin the web adversely affects both dryer operation and plate quality(i.e., staining of the emulsion). In addition the fibrous threads,characteristic of the absorbing web, tend to be picked up by therelatively soft emulsion during the drying process. Foreign materialattached to the plate 3,286,367 Patented, Nov. 22, 1966 would adverselyaffect the quality of prints produced from the plates. It is also knownin the art, to use heated platen devices for drying. However, it hasbeen observed that drying efiiciency in these devices is affected byuniformity of contact between the material to be dried and the platen.If an air space develops between the material and the platen, drying inthe area of the air space is inhibited resulting in non-uniform plates.Thus, prior art dryers do not produce practical, uniform,.rapid dryingat controlled low temperatures without physical damage to a relativelysoft emulsion coated offset plate material. p i

It is an object of this invention, therefore, to provide an improvedapparatus for drying photo-graphic type emulsion coated sheets whichavoids one or more disadvantages ofthe prior art.

his a further object of this invention to provide an improved apparatusfor drying photographic type emulsion coated sheets at a rapid rate andat relativelylow temperatures. 1

It is a further object of the invention to provide an improved dryer forphotographic type emulsion coated sheets that produces uniformdryingacross the face of the emulsion.

It is still a further object of the invention to provide an improvedapparatus for drying photographic type emulsion coated sheets whereinthe emulsion surface is unmarred during transportationthrough the dryer.I

In accordance with the present invention there is provided an improvedapparatus for drying photographic type emulsion coated sheets. Theapparatus comprises a housing having an inlet opening and a dischargeopening. A heated platen is disposed within the housing. A portion ofthe platen surface defines a path along which the sheets travel throughthe dryer. There is provided contact means for holding the sheets inintimate contact with the path defining portion of the platen. Thecontact means holds the sheets in contact with the platen as the sheetstravel along the defined path for causing heat conduction through thesheet to the emulsion coating. The contact means are spaced to permitvaporization of moisture from the emulsion. There are also providedmeans disposed along the path to accelerate vaporization of moisturefrom the emulsion coating after the moisture has been initially heatedby the platen. Transport means are provided for transporting the sheetin the defined path from the inlet along the platen, to the dischargeopening whereby the emulsion coated sheets are dried.

For a better understanding of the present invention together with otherand further objects thereof, reference is made to the followingdescription taken in connection with the accompanying drawings and itsscope will be pointed out in the appended claims.

FIG. 1 is a schematic illustration of the principles of operation of adryer embodying the present invention;

FIG. 2 is a perspective view, partially cut away of a dryer embodyingthe present invention;

FIG. 3 is a sectional view taken along line 33 in FIG.

2; and

FIG. 4 is an end view, partially in section, of another embodiment ofthe present invention.

Referring now in more detail to the drawings and with particularreference to FIG. 1 there is here schematically illustrated the broadprinciples of operation of the invention. The dryer broadly operates byfirst conducting heat to the moisture to be removed and thenaccelerating vaporization by forcing air against the preheated moisture.A typical material to be dried is designated by the numeral 10. Thismaterial, by way of example only, has four layers. An emulsion layer10a, a plastic coating Connects the pulley 41,to the cylinder 34a.

. 3 b, a carrier sheet 100, and a plastic coating 10d. The

sheet 1-0 is fed into the dryer housing 11 'so that the .16 controls theelectrical input (i.e., voltage), to the heat source. The platen sourceis maintained at a substantially constant temperature through a feedbackloop consisting of a sensor 14 and control 16. The sensor measures theplaten temperature while the control is set for a desired referencetemperature. The difference between the two temperatures causes'thecontrol 16 to energize or deenergize the heat source 13. A contact means18 maintains the sheet in intimate contact with the platen during aportion of its travel in the dryer, thereby preventing air spaces fromdeveloping between the platen and the sheet. Any air space would be alocal insulator causing nonuniform drying of this sheet. 7 has beenfound that most of the moisture in'this type of material, as it entersthe dryer, is in the emulsion. The material is squeegeed prior todrying, removing most of the moisture from the plastic coated exposedsurface. The contact means 18 is provided with perforations 21 forallowing the moisture to escape from the emulsion layer 10a. Theemulsion layer is heated by conduction of heat from'the platen 12through the, layers 10d, 10c, and 10b. The temperature of the emulsionsurface rises initiating vaporization of the moisture at the surface. Byway of example, the critical temperature beyond which Project-A-Lithemulsion can be heated is in the order of 17()190 F. A blower 19 ismounted in the housing 11 and blows ambient air in the direction Aagainst the emulsion surface to accelerate vaporization of moisturetherein. An exhaust system, shown by the exhaust fan 20, may be added tofurther accelerate vaporization. The exhaust fan continuously removesmoisture from the housing 11 in the direction B preventing the humiditylevel from rising therein.

Referring now in more detail to FIG. 2, there is here shown aperspective view, partially cut away, of the preferred embodiment of adryer embodying the present invention. The dryer is contained in ahousing generally As a practical matter, it

designated by the numeral 30. The housing has an inlet guide 33 fordeflecting and guiding the leading edge of the sheet to be dried towardsa rotatable cylindrical platen 34. The platen'34 has a cylindricalsection 34a and a pair of circular end plates 34b only one of which isshown in FIG. 2. 'Ihe end plates are fastened to the cylindrical section34a by means of screws 35. The end plates have bearings 36 mountedtherein. One bearing is shown in FIG. 2. Associated with each bearing 36is a snap ring'60 for preventing axial shifting of the platen assemblyalong shaft 37. The platen assembly is rotatable about stationary shaft37, which is secured to the housing 30. The assembly is rotated by meansof a motor 38 mounted on top of housing 30 in a motor housing 39. Achain drive connects the motor 38 to a sprocket 39 mounted on the end ofshaft 40. The opposite end of shaft 40 has a pulley 41 thereon aroundwhich is wrapped a garter spring 42. The garter spring 42 p The garterspring 42 is under tension therefore rotating platen 34 as pulley 41 isrotated. Also mounted on shaft 40 is a plurality of spaced rollers 43.As seen more clearly in FIG. 3 which is a vertical section taken alongline 33 in FIG. 2, the rollers 43 have endless belts 44 coupled thereto.The endless belts pass over rollers 45, 46, and 47 mounted on shafts 48,49, and 50 respectively. As the pulley 43 is rotated the portion of belt44 in contact with the platen 34 travels in the same direction as theplaten, thus transporting the paper in contact with the platen to allowheating of the sheet by the platen. Since the emulsion surface is soft,it is desirable that the belts 44 do not exert any excessive pressure onthe sheet during transport. Therefore, means are provided for adjustingthe tension in belts 44 by means of slots 63 disposed in oppositevertical walls of housing 30 (see FIG. 3 wherein one slot is shown).Shaft 49 is provided with the threaded ends 64 which protrude throughslots 63 allowing the tension to be adjusted by vertical alignment ofshaft 49. Nuts are used to clamp the shaft in place after alignment. Forthe sake of clarity, the means for rotatably mounting the shafts onthe'housing and the means for fixedly mounting the shaft 37 to thehousing have not been shown. Any of the means well known in the art foraccomplishing the desired result may be used. For example, the rotatableshafts may be mounted in sleeve bearings which are held in trunions onthe housing, the trunions for shaft 49 being adjustable vertically asthe shaft is adjusted. The stationary shaft 37 may be bolted to thehousing. The platen is heated by a heat source 51 which may for examplebe an infrared lamp, which is coupled toshaft 37 by two brackets oneither end of the shaft, one of which is'shown at 52. The belts 44 arepreferably porous to allow moisture to pass therethrough,and spaced toleave a maximum area on the sheet material exposed to the housingenvironment for the purpose of vaporizing moisture from the surfacethereof. To accelerate vaporization, a blower 53 is mounted in thehousing 30. The blower 53 forces ambientair against the exposed surfaceof the sheet thus accelerating vaporization of moisture on the exposedsurface which. has been initially heated by conduction from platen 34.An exhaust fan 54 may be provided for removing accumulated moisture fromthe housing 30 thus controlling the humidity level therein. The exhaustfan 54 is also mounted in the housing30. A temperature sensor 60, whichmay be a thermocouple or thermistor is coupled to the platenfor'providing an indication of the platen temperature. This'co-operateswith a control device as was explained with reference to FIG. 1. Shaft40 is provided with a plurality of pulleys 43 supporting endless belts55 disposed between the belts 44 for transporting paper from the platentowards the exit opening 32. The endless belts 55 are disposed about IThe operation of the dryer will be explained with reference to FIGS. 2and 3.

Prior to use, the platen 34 is preheated by energizing the heat source51. The motor 38 is energized causing the chain drive to drive sprocket39 in the direction of arrow C shown on shaft 40. The sprocket 39 inturn drives shaft 40 in the same direction causing belts 44 to move inthe direction of arrow E and the platen 34 to rotate in the direction ofarrow E. The belts 55 move in the direction of arrow F.

The photographic emulsion is fed into the dryer through the inletopening 31 with its emulsion side down. The leading edge of the sheetcontacts guide 33 and is directed towards the platen 34. The leadingedge, thereafter, engages the portion of belts 44 in contact with theplaten on the side nearest the inlet opening 31. The sheet is thentransported in contact with the rotating platen toward the exit side ofthe dryer. During transport along the platen, the emulsion surface isaway from the platen whereby moisture in the emulsion is heated by heatconduction through the platen to the emulsion surface. As the sheetreaches the vicinity of blower 53 ambient air is forced against theemulsion surface by the blower accelerating vaporization of the moisturethat has been preheated by conduction from the platen. In order toachieve maximum vaporization of the moisture from the sheet, belts 44are porous and spaced. The sheet coutinues to travel in the dryer untilthe leading edge engages the guide 59 at which point the sheet isdirected toward the exit opening 32. The leading edge travels along theguide 59 until it passes between spring 61 and belt 55. The sheet isthen driven through the exit opening by the combination of belt 55 andspring 61. The sheet emerges from the dryer with its emulsion side down.An exhaust fan 59 removes air from the housing. The removal of air fromthe housing lowers the humidity level as well as lowering the housingtemperature. Lowering the housing temperature causes a greatertemperature drop across the platen and sheet increasing the amount ofheat flow therethrough at a given input temperature.

Another embodiment of the invention in FIGS. 2 and 3 is illustrated inFIG. 4. In this embodiment a receiving bin 62 is mounted on the rearwall of the housing 30. As the sheet emerges from the dryer through theexit opening 32, with its emulsion side down, it slides down the rearwall of bin 62. As the sheet lies in the bin, the emulsion side would befacing the discharge of the exhaust blower 54. Although this air fromthe exhaust blower is slightly damp, it is heated and it has been foundto be useful in further drying the sheets.

While we have described what is presently considered a preferredembodiment of our invention, it will be obvious to those skilled in theart that various changes and modifications may be made therein withoutdeparting from the inventive concept, and it is aimed in the appendedclaims to cover all such changes and modifications as fall within thetrue spirit and scope of our invention.

What is claimed is:

1. In a dryer for drying sheet material:

(a) a curved platen having a sheet contact surface associated therewith;

(b) a plurality of spaced flat sheet transport belts;

(c) means for causing said flat belts to contact the sheet contactsurface associated with said curved platen, the ratio of the sum of thewidths of said flat belts over the width of said sheet contact surfaceof said platen being such as to leave wide spaces between said belts forthe purpose of vaporizing moisture therefrom;

(d) means for driving said belts to cause said sheet material to betransported through said dryer between said curved platen and saidbelts, and

(e) means for causing drying gas to pass over at least a portion of saidsheet contact surface of said curved platen to accelerate the drying ofsaid sheet material.

2. The combination as set forth in claim 1 wherein said belts are madeof non moisture absorbent material having apertures formed therethroughfor allowing vapor to escape from said sheets through said apertures.

3. The combination as set forth in claim 1 further including a sheetreceptacle means for receiving sheet material emerging from said dryerand means for directing said drying gas from the interior of said dryerto said receptacle to further dry said sheet material present there- 4.The combination as set forth in claim 1 wherein means are provided forheating said curved platen.

5. The combination as set forth in claim 2 wherein means are providedfor heating said platen.

6. The combination as set forth in claim 1 wherein said means fordriving said belts also drives said platen at the same tangentialvelocity as the velocity of said belts.

7. The combination as set forth in claim 2 wherein said means fordriving said belts also drives said platen at the same tangentialvelocity as the velocity of said belts.

References Cited by the Examiner UNITED STATES PATENTS 1,794,063 2/1931Dye 34-ll1 2,596,358 5/1952 Ball 34114 X 2,895,395 7/1959 Gern 34-116 XFREDERICK L. MATTESON, JR., Primary Examiner.

A, D, HERRMANN, Assistant Examiner.

1. IN A DRYER FOR DRYING SHEET MATERIAL: (A) A CURVED PLATEN HAVING ASHEET CONTACT SURFACE ASSOCIATED THEREWITH; (B) A PLURALITY OF SPACEDFLAT SHEET TRANSPORT BELTS; (C) MEANS FOR CAUSING SAID FLAT BELTS TOCONTACT THE SHEET CONTACT SURFACE ASSOCIATED WITH SAID CURVED PLATEN,THE RATIO OF THE SUM OF THE WIDTHS OF SAID FLAT BELTS OVER THE WIDTH OFSAID SHEET CONTACT SURFACE OF SAID PLATEN BEING SUCH AS TO LEAVE WIDESPACES BETWEEN SAID BELTS FOR THE PURPOSE OF VAPORIZING MOISTURETHEREFROM; (D) MEANS FOR DRIVING SAID BELT TO CAUSE SAID SHEET MATERIALTO BE TRANSPORTED THROUGH SAID DRYER BETWEEN SAID CURVED PLATEN AND SAIDBELTS, AND (E) MEANS FOR CAUSING DRYING GAS TO PASS OVER AT LEAST APORTION OF SAID SHEET CONTACT SURFACE OF SAID CURVED PLATEN TOACCELERATE THE DRYING OF SAID SHEET MATERAIL.